1. Field of the Invention
The invention is related to electromagnetic fluid pumps and in particular to metering fluid pumps having a controllable fluid output.
2. Description of the Prior Art
Reciprocating electromagnetic fluid pumps, such as those taught in L.C. Parker in U.S. Pat. No. 2,994,792 and E.D. Long in U.S. Pat. No. 3,361,069, used mechanical or magnetic switches to energize a solenoid to retract the piston or plunge when it reaches the end of its pumping stroke. These switches were unreliable and, therefore, their use has been discontinued. Currently, most of these reciprocating electromagnetic fluid pumps use electronic oscillators which energize the pump's solenoid at predetermined intervals. Some of these pumps use free-running oscillators, as taught by Kofinh in U.S. Pat. No. 3,211,798, or a blocking oscillator, as taught by Wertheimer in U.S. Pat. No. 3,381,616. Pumps with electronic oscillators operate at a constant speed and work well for a narrow band of output loads.
The invention is a low pressure metering fluid pump particularly suited for providing fuel to wick or carburetor type burners to control the heat output, as a function of an operator control or a temperature sensor.